Hi Cajaf,
Aside from being a Google Answers researcher, I'm also a translator
and I used my contacts on this one. I asked some Thai friends of mine
who are also professional translators for their comments. Below is the
summary of our communication:
"Klai klai gan" means "same" or "same, same"
"Meuan meuan tair daang gan" means "Same, same but different (exact
literal translation).
According to them "Meuan meuan dair daang gan" is a literal
translation. It should rather be "Meuan gun tair taang gun". It also
means "Same, same but different" but they say that this is a better
translation. I think this one is what you are looking for.
They also told me that "tair" is the proper word not "dair". So the
example given in the comment below, "Meuan gun DAIR daang gun" should
be "Meuan gun TAIR daang gun"
Another suggestion is "Mai chai tair klai kiang" which means "It's
not, but it's close" -- basically an interpreted translation of the
original English source. They prefer this one than the other
translations.
Search strategy:
Consulted with Thai friends.
If you have a question, please feel free to post your clarification
before rating this and I'll attend to you as soon as possible. Thanks
for visiting us and I hope you become a frequent and happy user of
Google Answers.
Best regards,
Feilong

"klai klai gan" means "similar to" (with out 'but differnt')
tutuzdad-ga's answer would literally translate as "one of a kind
different" (with no 'but')
A good translation would be
"meuan meuan dair daang gan"
or
"meuan gun dair daang gun"
However, it would probably just confuse Thai people becasue they
wouldn't understand the joke, or those that did know the joke would
probably not be able to re-translate the Thai back into the original
English to get the joke.
Regards,
Neil
(3rd year student studying Thai language at SOAS London)

Neil
Glad to know that you are studying Thai
You try to translate it directly to English
"Same, same but different"
to
"meuan meuan dair daang gan"
I see your point
BUT actually "we" will confuse when we hear it

The reason why translating "Same, same but different" to Thai is
confusing is because it has no grammatical meaning in English so
without any addition of context, how would it possible to translate
the phrase into Thai and somehow gain a meaning?
Another nonsensical example: ?Big, big but small!?

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